In the search for suitable friction materials for high-performance brake systems using ceramic friction bodies, the conventional organically bound friction materials reach their limits because of the high temperatures and high wear rates which occur. This becomes particularly apparent in the case of friction pairings in which C/SiC or C/C—SiC is used as brake disc material. These materials are ceramics formed essentially of SiC and secondary phases comprising Si and C, which is reinforced with carbon fibers, for example as described in DEA 197 10 105. During braking, temperatures around and above 1000° C. occur at the friction surface, and organically bound brake linings consequently decompose.
In EP-A 1 079 137, a sintered metal material is proposed for brake linings which, in combination with C/C-SiC brake discs, leads to an increased operating life and improved frictional behavior and consists of a sintered copper material having a mass fraction of more than 60% of copper. However, inter alia, the high-temperature strength required for ceramic friction partners is restricted by the high copper content and the binder phase.
In DE-A 197 27 586, it is proposed to use a combination of a C/SiC brake disc and a corresponding C/SiC brake lining. The C/C intermediate body for the brake disc has a density which is lower than that of the surface regions of the C/C intermediate body for the brake lining. This leads to a C/SiC having a relatively low strength being formed after the liquid silicization of the C/C intermediate body for the lining. However, the overall frictional and wear behavior, the performance when wet and in particular the comfort characteristics, including constant coefficients of friction and low noise, are not yet satisfactory.
In view of this prior art, it is an object of the invention to provide a friction material which withstands the high temperatures during braking without suffering damage and displays improved comfort characteristics in combination with ceramic counterbodies. In particular, the friction material should be matched to the combination with C/SiC brake discs.